Collaborative Research: Interaction Between Plumes and Surface Waves from the Surf Zone to the Inner-Shelf

河流在向沿海海洋输送陆源物质(例如，沉积物、污染物)和淡水方面发挥了重要作用，后者影响了沿海循环。然而，近岸海浪和海浪破碎在烟柱混合、输送和海岸线最终命运中的作用尚不清楚。为了解决这一知识差距，该项目使用测量和数值模型相结合的方法来确定沿海海洋中漂浮的河流羽流水的命运。来自两个现场实验的观测将测量河流羽流在沿海海洋中的扩散和混合。这些现场的真实模拟与理想化的数值模拟相结合，将允许实验跨越广泛的参数空间，以便与跨越各种海岸线的不同类型的河流相关。这项工作将导致对河水混合和沿海海洋命运的更好理解，这对于量化沉积物、污染物、幼虫和其他重要物质在近岸的扩散至关重要。因此，这项工作将有助于确定相关的空间和时间尺度，以减轻在不同条件下因沿海水质差而产生的风险，改进沿海水质预测，并减少人类对受污染水域的暴露。这项研究将加深对有限深度表面波作用下小开尔文数、中小流量河流羽流的动力学理解。先前的研究表明，波浪对羽流结构和混合有重要影响，但在理解各种河流排放和冲浪带/内陆架区域的波浪/羽流相互作用方面仍存在重大知识空白。这些知识差距限制了我们预测小河流及其携带的物质最终命运的能力，这些物质与海岸污染、幼虫运输等有关。初步模拟表明，存在着显着的波浪驱动的羽流修正，包括加强了海浪带内的沿岸扩散，减少了对内陆架的淡水输出。一套理想的耦合海洋环流和波浪传播模式，模拟了不同的河流流量、波高、波向、潮位和科里奥利强迫，将为探索波浪和羽流的相互作用提供参数空间。理想化研究的结果将用现有研究地点(现有观测和现实模型输出)和新的补充研究地点的结论加以补充。新研究地点的观测活动和现实模拟旨在捕捉现有地点没有捕捉到的缺失参数空间和羽流指标。最后，将对一套理想化和现实化的模型和观测数据集进行组合分析，以解决四个关键假设。最终，这项研究将：(1)确定将羽流水困在海浪带内的物理机制，(2)表征河流与海浪动量通量在烟羽范围内的作用，(3)确定困在海浪带的淡水被输送到内陆架的途径，以及(4)在浮力梯度存在的情况下，在深度受限的波浪破碎区域测试现有的湍流闭合模型。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Rivers play an important role in delivering land-derived material (e.g., sediment, contaminants) and freshwater to the coastal ocean, the latter impacting coastal circulation. Yet the role of near-shore waves and wave breaking in plume mixing, transport, and ultimate fate along the coastline is not yet understood. To address this knowledge gap, this project uses a combination of measurements and numerical models to determine the fate of buoyant river plume water in the coastal ocean. Observations from two field experiments will measure river plume spreading and mixing in the coastal ocean. Realistic simulations of these field sites combined with idealized numerical simulations will allow the experiment to span a broad range of parameter space in order to be relevant to different types of rivers across a variety of coastlines. The improved understanding of river water mixing and fate in the coastal ocean that will result from the work is crucial to quantifying the spreading of sediment, pollutants, larvae, and other important material in the nearshore. Thus, this work will aid in identifying the spatial and temporal scales relevant to mitigating risks due to poor coastal water quality under varying conditions, improving coastal water quality predictions and reducing human exposure to contaminated waters. This study will improve the dynamical understanding of small Kelvin number, small-moderate discharge river plumes in the presence of depth-limited surface waves. Prior research has shown important wave impacts on plume structure and mixing, yet significant knowledge gaps remain in the understanding of wave/plume interactions across a range of river discharge and across the surf zone/inner-shelf region. These knowledge gaps limit our ability to predict the ultimate fate of small rivers and the material they carry with them, relevant to coastal pollution, larval transport, and more. Preliminary simulations suggest there is significant wave-driven plume modification including enhanced along-shore spreading within the surf zone and decreased freshwater export to the inner-shelf. A suite of idealized coupled ocean circulation and wave propagation model simulations for varying river discharge, wave height, wave direction, tidal stage, and Coriolis forcing will provide a parameter space to explore wave/plume interaction. The results from idealized studies will be augmented with conclusions from an existing study site (with existing observations and realistic model output) and a new complementary study site. The observational campaign and realistic simulations of the new study site are designed to capture the missing parameter space and plume metrics that were not captured at the existing site. Finally, combined analyses of the suite of idealized and realistic models and observational datasets will be done to address four key hypotheses. Ultimately this study will: (1) Determine the physical mechanisms that trap plume water within the surf zone, (2) characterize the role of riverine versus wave momentum fluxes on plume extent, (3) identify pathways through which freshwater trapped in the surf zone gets exported to the inner shelf, and (4) test existing turbulence closure models in the region of depth-limited wave breaking in the presence of buoyancy gradients.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.